Digital Infrared Photography at 14,000 ft, Part 2

July 09, 2014  •  Leave a Comment

For a recent hike up Mt. Shavano in Colorado (14,229 ft), I decided to bring along only my infrared-modified old Canon T2i and 10-22mm lens. If you're just jumping in, check out part one of this post.

So here's what things look like with the 780 nm infrared filter (aka Wratten 87) when left in color.  At about 720 nm and deeper (longer wavelenths, e.g. 780 nm, 900 nm, etc.), you need to perform a custom white balance off of green vegetation.  It needs to be vegetation because it's the chlorophyll that reflects in a particular infrared "color" that you're keying off of.  Something green that is not foliage won't work.

This custom white balance will result in the classic white foliage of infrared photography, and when using cutoffs such as 720 nm and 780 nm you'll get a bronze sky.  The effect will be slightly more pronounced at 720 nm than you see here at 780 nm.  You may see some bluish tones on certain objects.  If those are undesirable, simply drop the luminance of that blue hue in Photoshop or Lightroom.  Note that if you're shooting RAW, ACR (Adobe Camera RAW, the engine behind Photoshop and Lightroom for interpreting RAW images) can't handle the bizarro embedded white balance.  You can go through some crazy juju for slapping it around and getting it to work (it involves making a custom camera profile using Adobe's DNG Profile Editor, but that's a whole 'nother post), but it's much simpler to shoot in JPG so that the proper white balance is embedded.  This is the one time I'll shoot in both RAW+JPG so I can see what it should look like and perhaps just use the JPG but have the option of using the greater dynamic range of the RAW.  These shots below are from RAW and you can see some inconsistency in my guesswork with the white balance.  It's not entirely my fault, however, as you will notice the sky looking different depending on the camera angle relative to the sun, much as you would see when using a polarizing filter with visible light.

False-color 780 nm digital infrared photography near Mt. ShavanoFalse-color 780 nm digital infrared photography near Mt. Shavano

Now, as luck would have it, this bronze color in the sky turns into a somewhat believable blue sky when you swap the red and blue channels of the image in Photoshop and get some real fairytale-lookin' stuff.  The shade of the sky can rapidly go askew if you didn't handle your RAW white balance voodoo properly, and I'm still struggling with getting it just right.  In most of these below, I wound up shifting the sky slightly towards magenta to compensate for them being slightly green due to my initial misjudgment in my RAW processing.  You'll also wind up with a slight yellow in the foliage (which comes from the a slight blue prior to the red/blue channel swap), and it's up to you if you want to keep it or desaturate it to white.  I left some yellow and desaturated others in these images below.  In my next post I'll show how you can do some really crazy stuff with the channel swap when shooting with a 665 nm filter which lets in even more visible light.

False-color 780 nm digital infrared photography near Mt. ShavanoFalse-color 780 nm digital infrared photography near Mt. Shavano with a red/blue channel swap performed in Photoshop

 


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